Hydraulic Characteristics And Coordinations Between Leaf And Stem In Machilus Species

Machilus species are evergreen basal angiosperms belong to family Lauraceae,which have relatively high ecological and economic value.The study on the functional characters of the Machilus is helpful to understand the origin and evolution of the basal angiosperms.In this study,the water and photosynthetic parameters of seven species of the tree were determined.We try to understand the relation between leaf water supply and demand as well as the relation between xylem anatomy characteristics and hydraulic efficiency,and provide reference for further study of ecophysiological adaption and cultivation.The results are as follows:(1)In leaf hydraulic characteristics.Vein density of these seven Machilus species was much higher than other primitive angiosperms,within a moderately high range(9.8?14.1 mm/mm2),and significant positive relationship between stomatal density and vein density was found,indicating correlation of leaf water supply and demand;stomatal density was negatively correlated with stomatal size;leaves with larger stomata were less resistant to water loss.(2)In the hydraulic characteristics of branches.The better the reinforcement degree of the conduit wall,the higher the conduits density,and the smaller the cross-sectional area of the conduits.Stem sapwood specific hydraulic conductivity was relatively low(0.13?1.87 Kg·mm-1·s-1·MPa-1),with large interspecific variation.No significant relationship was found between Ks and pit membrane area,pit aperture area and the ratio of pit aperture length to width.Therefore,the relationship between the pit membrane and water transport is not well explained by the area characteristics of a single pit.(3)Vein density and stomatal density were positively correlated with Ks,reflecting the coordination of water relation between plant leaves and stems.The characteristics of the conduits are to some extent synergistic with the drought resistance of the leaves.The xylem anatomical structure was still primitive with low hydraulic efficiency,which can only adapt to rather humid habitat.